Field of the Invention
This invention relates to containers of the kind used for the transport of freight in so-called `container-ships`, or by rail or by road. Such containers are made to one of a few internationally agreed sizes and have caused great changes in the practice of cargo handling over the past 10 years or so. Proposals have been made from time to time for collapsible containers so that when there is an imbalance of trade between two points, empty containers can be collapsed to occupy a quarter or a fifth of the height of an erect container and so fewer ships, trains or lorries are required to return empty containers than to carry revenue-earning full containers. None of the proposed collapsible containers has yet had an impact on containerized freight handling.
There are several problems which a collapsible container must overcome to be satisfactory. Firstly it must comply with the dimensional tolerances specified by the agreed international standards. It must do so both when erect and when collapsed, (or at least a stack of collapsed containers must fit the dimensions laid down for an ordinary container). Secondly a container must be robust. A rigid container must withstand a fair amount of wear and tear from handling in transit which a collapsible container must be able to withstand as well. But a collapsible container must also be robust and simple to operate in its collapsing and re-erecting. Thirdly, there is always the question of cost. A collapsible container is bound to cost more than a rigid one but if its costs are too much greater than those of a rigid one than it will not be worth the savings available from return journeys in the collapsed position.